1. Field of the Invention
The present invention relates to a resist lower layer film composition for a multilayer resist film used for microfabrication in a process for manufacturing semiconductor devices etc., and particularly relates to a resist lower layer film composition suitable for exposure by far ultraviolet ray, KrF excimer laser light (248 nm), ArF excimer laser light (193 nm), F2 laser light (157 nm), Kr2 laser light (146 nm), Ar2 laser light (126 nm), soft X ray, an electron beam, an ion beam, X ray and the like. Furthermore, the present invention relates to a patterning process for patterning a substrate using the resist lower layer film composition with lithography.
2. Description of the Related Art
In recent years, with advanced high integration and speed up of LSI, it has been required to make a pattern rule finer. In such a circumstance, in lithography using light exposure currently used as common technology, an essential resolution derived from a wavelength of a light source has been approaching a limit.
There is widely used optical exposure using g line (436 nm) or i line (365 nm) of a mercury-vapor lamp as a light source for lithography when a resist pattern is formed. It has been considered that a method of using an exposure light with a shorter wavelength is effective as a means for obtaining a further finer pattern. For this reason, for example, KrF excimer laser (248 nm) with a shorter wavelength is used as an exposure light source instead of i line (365 nm) for mass-production process of a 64 M bit DRAM processing method. However, a light source with far shorter wavelength is needed to manufacture DRAM with integration degree of 1 G or more which needs still finer processing techniques (for example, a processing size is 0.13 μm or less). Accordingly, lithography with ArF excimer laser (193 nm) has been particularly examined.
As the resist film has been made thinner, materials capable of being etched at a considerably higher speed are required for ordinary organic antireflection films compared with the resist. The organic antireflection film where the etching speed is enhanced by changing a base resin from a novolak type to a (meth)acryl type and further to a polyester type has been developed.
In the resist pattern after the exposure and the development on a mask substrate of Cr and the like, in the positive type photoresist, a problem that a substrate interface becomes a footing profile has occurred. It is believed that this is caused by diffusing the acid generated in the photoresist due to the exposure in the mask substrate of Cr or the like to reduce an acid concentration in the photoresist near the substrate. In order to reduce the occurrence of the footing profile, the improvement has been performed by using a protecting group having a low activation energy for a deprotection reaction with the acid, but this is not sufficient. To reduce the occurrence of the footing profile, it is effective to use an organic film between the photoresist and the Cr substrate.
An antireflection function is necessary in the case of the optical exposure, but in depiction of the mask pattern, the antireflection function is not particularly needed because the electron beam (EB) is used. Required are an excellent acid block function and a high etching speed for not diffusing the acid generated in the photoresist to the substrate.
Here, a resist lower layer material containing a polymer having α-hydroxymethyl acrylate as a repeating unit is disclosed (see Japanese patent Lapid-open (Kokai) No. 2007-17949). However, an organic film which has the higher etching speed has been required.